It may or may not be bad, I'm not sure. But you are sucking air in from somewhere. And since it was not there before you opened the lid. Logic would dictate that you did not reseat properly. I would suggest starting over. Open the lid inspect/clean the gasket/o-ring, re-seat and tighten secure. If you still get air, take a hose and flush water around the lid and other areaslike the drain plug to see if the bubble goes away. Another way is to light a cigar and and run around lid and other fittings to see if smoke gets sucked in.